Question

Which one of the following alkaline earth metal carbonates is thermally the most stable?

• A. $MgC{O}_3$
• B. $CaC{O}_3$
• C. $SrC{O}_3$
• D. $BaC{O}_3$

Answer 1

The correct option is D $BaC{O}_3$

Barium carbonate is thermally the most stable. On moving down the group, the electropositive character of alkaline earth metals increases. Due to this, their thermal stability also increases. The smaller the positive ion, the higher the charge density, and the greater effect it will have on the carbonate ion. As the positive ions get larger down the group, their affect on the carbonate ions near them decreases. More heat must be supplied for the carbon dioxide to leave the metal oxide. In other words, the carbonates become more thermally stable down the group. Hence, $BaC{O}_3$ is the most stable.